The CARDIORISK consortium will develop a series of experimental systems to study the radiation biology of cardiovascular effects. Both in vivo and in vitro model systems will be deployed to describe and quantify the effects of ionizing radiation occurring at low doses. The knowledge gained will provide the impetus necessary to place radiation protection considerations of late cardiovascular effects in a biological context. The project will also be of direct benefit in modelling strategies that aim to extrapolate cardiovascular risk from epidemiological studies.
Cardiovascular diseases and cerebrovascular diseases are examples of obvious multicellular origin. This notion implies, that radiation-induced organ damage only happens after radiation exposure has exceeded a threshold. This assumption has been challenged by recent epidemi-ological evidence on cardiovascular radiation mortality of the A-bomb survivors. In this population group, cardiovascular mortality has increased even after low dose radiation expo-sure without a clear cut threshold. The resolution of this problem is of considerable impor-tance for radiation protection since, because it requires a re-assessment of the current risk es-timation system for so called deterministic radiation effects (i.e. late organ damage). Only full knowledge of the pathogenic pathways is likely to offer a sound scientific basis for solving the question of possible dose threshold for radiation-induced cardiovascular risk at low radia-tion doses.
The main problems for the incorporation of the new epidemiological evidence of radiation-induced late cardiovascular and cerebrovascular damage arise in the definition of dose and the shape of the dose response relationship.
Only radiobiological experiments such as those planned within CARDIORISK described in this research project may be able to address the question of how to define radiation dose in the heart in situations of inhomogeneous radiation exposure which are the rule in particular in di-agnostic radiology.